Saturday, 28 April 2012

Something from nothing

I read an interesting blog post by a fellow named Richard Carrier the other day. In it he discusses the common idea that the universe was created from nothing, and what that might mean.

After all, a common question is why should the universe exist at all? Why is there something rather than nothing? One explanation is that God must have created the universe. Another is that for some reason nothingness is somehow unstable and will always lead to something.

And, quite apart from this question, creation from nothing is a common religious theme. It is also commonly assumed by the non-religious that all matter, time and space were created in the big bang, essentially from nothing. As such, perhaps it's worth thinking about what might happen if we can imagine such a state of nothingness.

There are various types and degrees of nothing -- empty space for one. However, it's not really nothing as quantum mechanics tells us that empty space is a seething foam of virtual particles popping in and out of existence randomly. It could be that one such fluctuation might be large enough to kick off a universe. It doesn't matter if this is infinitessimally unlikely -- if time runs for an infinite length of time then any possible event, no matter how improbable, is sure to happen in the end.

There are other physical explanations based on natural law that account for the spontaneous creation of universes. Certain formulations of M-theory also provide this prediction.

This is the kind of explanation used by physicists such as Lawrence Krauss and Stephen Hawking to describe how the universe could come into being spontaneously.

Unsurprisingly, those who want to prove that God exists by invoking the need for a creator aren't satisfied with this, and, as it happens, neither am I. When theists say "God did it", atheists often ask them "Then who created God?". To insist that the universe came into existence as a consequence of natural laws poses exactly the same problem: where did these laws come from?

So, perhaps empty space is not what we mean by nothing. Imagine instead empty space, except without the laws of quantum mechanics or M-theory. Actually, while we're at it, why should there be any physical laws at all? Let's just strip out all the laws of nature leaving only empty space.

Why stop there? Where does space, with its three dimensions come from? Scrap that too, and time while we're at it.

Perhaps now we've truly reached a state of pure nothingness. This is where it gets interesting.

Carrier argues that if such a pure state of nothingness ever existed (and he admits there is no reason to believe it ever did), then this would be unstable simply because if there are no physical laws, then there is no law preventing the spontaneous creation of a universe. Why not have one pop into existence? And in fact, why stop there? Why not have two universes, or three or four? In fact, if we assume that any number of universes is as likely as any other, it turns out that it is a mathematical necessity that there will be an infinite number of universes created.

Carrier is very impressed with this result. If there are infinite universes, then we needn't be surprised that this universe seems so much more hospitable to life than it might have otherwise been. This is because living beings who ponder these questions will by definition always find themselves in the tiny minority of universes that are capable of sustaining life (the anthropic principle). This has such explanatory power to Carrier that he admits that he is almost persuaded that this really is how the universe came into existence.

I don't buy it.

I suspect that this concept of true nothingness isn't really all that coherent. It's hard to prove that this is true, but there are a number of arguments that make me quite skeptical. For one, I'm not sure that the absence of all laws really allows universes, or anything else, to spring into existence. While there might not be any laws specifically saying they shouldn't, neither are there any laws saying they should.

First, lets look at some intuitive arguments.

If I wrote a computer program, giving it no instructions, it would do nothing. It wouldn't go off inventing universes with wild abandon, free at last from the shackles of its programming. Unfortunately, this isn't a persuasive argument, it's more of an observation indicating why my intuition (as unreliable as human intuition is) rebels against Carrier's argument. As Carrier might point out, even an empty computer program is not true nothingness.

However, for a scientific concept to be totally coherent, I suspect it should be possible in principle to write a computer simulation or mathematical description of it. Even an abstract concept such as love should be amenable to simulation, in principle at least. We could for example run a computer simulation of two complete human lovers -- all the way down to the atoms in their brains if necessary. I can't even begin to conceive of simulating Carrier's nothingness where anything can happen and there are no rules. The very absence of rules is what leads me to suspect that the concept is incoherent.

Let's try to think of a more rigorous argument.

For something to spring into existence, it implies a concept of time. First there were no universes, then there was one (or two, or three, etc). If there's true nothingness, then there's no time for anything to spring into existence. There's no change. Not even time itself can spring into existence. If we start with the assumption of nothingness, then it seems to me that that's what we're stuck with.

But maybe you could make some argument that we don't need time for things to spring into existence. Maybe our insistence that events can only take place within a temporal framework is spacetime chauvinism. Carrier responds to comments suggesting that his argument presupposes the existence of time by saying that there is no time in his framework -- universes are created instantly. I find this to be in contradiction to the initial premise that nothing exists. If universes exist the moment we consider the concept of nothingness, then we are not really considering the concept of nothingness, because there was never a "time" when there was nothing.

I have suggested this argument to Carrier in a comment on his blog (currently awaiting moderation):

I think the issue of time does reveal a possible contradiction in the argument, though.
You postulate the state that nothing exists, and then derive the state that infinite universes must exist.
Without time, we cannot move from one state to another state, and the two states are in clear contradiction.
I would argue that without time, then all events are logically impossible (as events are points in spacetime), including anything popping into existence, therefore there is in fact a logical reason preventing the spontaneous generation of universes even in a state of pure nothingness.

I have some other, less rigorous arguments too.

Once the first universe exists, then we are no longer in a state of nothingness. We now have physical laws which would likely preclude the creation of further universes. We can no longer use the anthropic principle to explain fine-tuning. Again, there is a reasonable objection. Carrier might argue that the laws of the newly created universe would be internal to that universe and would not affect the meta-reality that is our pure state of nothingness. He might be right, but I don't see why he is assuming that nothingness is more likely to spawn a child universe instead of simply becoming a universe itself. I suspect the answer he would have with this argument is that why don't we allow the state of nothingness to "become" two universes simultaneously, and therefore any number of universes.

Ok, so if whole universes can spring into existence, then why not physical laws? Why suppose that a universe is more likely to pop into existence than a law that says that nothing (further) can pop into existence spontaneously? The latter certainly seems simpler than the former, and so perhaps more likely to arise spontaneously. I'm probably not really justified in making that assertion as reasoning about probabilities in such an unconstrained anything-goes reality seems impossible.

Anyway, to put it in other words, if there's nothing preventing spontaneous creation of universes, there's nothing preventing the prevention of spontaneous creation either.

Carrier has provided one concept of nothing, but I believe there are others just as valid, if not more so. Is it not conceivable that the universe might simply exist in a dead state, devoid of time and space and where nothing ever happens, including spontaneous creation of universes? If this is not true nothingness, because there is a law prohibiting spontaneous creation, then I think our disagreement is semantic. I'm not sure I like Carrier's definition of nothingness either because it implies that there is a law which mandates spontaneous creation.

But if we allow that Carrier's concept of nothingness could have once been the state of the universe, why not allow that the dead state also could have been? Then we are still left asking, why were we lucky enough that the universe was initially a creative one rather than a dead one?

However, there are some aspects of Carrier's argument with which I am in emphatic agreement. I agree with him that there are infinite universes, and that this is the best explanation for fine-tuning. I also think that the proper way to attempt to explain why something exists rather than nothing is with philosophical or mathematical arguments such as this one. Carrier explains that he is an empiricist, and so am I in general, but I can't help feeling that empirical science can only ever hope to discover what the fundamental laws of the universe are. It cannot explain how they came to be in the first place, or why they should not be otherwise.

This brings me to my final reason for skepticism of Carrier's argument. This reason is personal, and frankly, this is what really motivates me to find reasons to disagree with him. It happens that I have my own pet philosophical argument for why there should be infinite universes, an argument I find completely persuasive. Carrier's argument is redundant because my argument (in my opinion) provides a better and more intuitive explanation. I hope to write this up in a future blog post.